Method and apparatus for the production of blocks from sodium hydroxide solution

ABSTRACT

1. A METHOD OF PRODUCING SOLID BLOCKS FROM A LIQUID SUCH AS MOLTEN SODIUM HYDROXIDE, COMPRISING THE STEPS OF PROVIDING AN UPRIGHT SHAFT OPEN AT BOTH ENDS; INITIALLY BLOCKING THE LOWER END OF THE SHAFT; FILLING THE SHAFT TO A PREDETERMINED LEVEL WITH THE LIQUID; POSITIONING AT LEAST ONE STATIONARY DOWNWARDLY TAPERED COOLING ELEMENT AND AT LEAST ONE UPWARDLY AND DOWNARDLY MOVABLE DOWNWARDLY TAPERED COOLING ELEMENT IN THE LIQUID AT THE UPPER END OF THE SHAFT; COOLING THE LIQUID IN THE SHAFT TO FORM A SOLID; UNBLOCKING THE LOWER END OF THE SHAFT; SUPPLYING THE LIQUID TO THE SHAFT ABOVE THE FORMED SOLID; AT LEAST PARTIALLY RETRACTING EACH MOVABLE COOLING ELEMENT UPWARDLY FROM THE SOLID FOR FLOW OF THE LIQUID INTO THE SPACE BETWEEN EACH MOVABLE COOLING ELEMENT AND THE SOLID TO SOLIDIFY THE LIQUID IN CONTACT WITH EACH MOVABLE COOLING ELEMENT; THEN MOVING EACH MOVABLE COOLING ELEMENT AND THE WARDLY TO FORCE THE SOLID DOWNWARDLY IN THE SHAFT TO LEAVE A SPACE BETWEEN EACH STATIONARY COOLING ELEMENT AND THE SOLID FOR RECEIPT AND SOLIDIFICATION OF ADDITIONAL LIQUID IN CONTACT WITH THE STATIONARY COOLING ELEMENT; EACH STATIONARY COOLING ELEMENT BLOCKS UPWARD MOVEMENT OF THE SOLID DURING RETRACTION OF EACH MOVABLE COOLING ELEMENT UPWARDLY OF THE SHAFT; AND CYCLICALLY REPEATING THE UPWARD AND DOWNWARD MOVEMENT OF EACH MOVABLE COOLING ELEMENT TO FORCE A CONTINUOUS LENGTH OF THE SOLID OUT OF THE LOWER END OF THE SHAFT.

Nov. 26, 1974 H. KUHNLEIN 3,851,035

METHOD um APPARATUS FOR THE PRODUCTION OF BLOCKS FROM SODIUM HYDROXIDE SOLUTION Original Filed Nov. 27, 1970 United States Patent US. Cl. 264-148 5 Claims ABSTRACT OF THE DTSCLOSURE A method for forming solid blocks from sodium hydroxide solution comprises supplying molten lye by gravity feeding to a vertical cooling shaft and cooling the solution from above in repeated incremental steps while ejecting the solidified extrusion from the shaft downwardly. The cooling and the ejection are carried out by the displaceable downward movement of cooling elements, including fixed and movable elements. After each cooling step, the movable elements are retracted and the shaft is filled up to the original level with the sodium hydroxide solution. During each subsequent step at least a portion of the refill melt present between the solidified extrusion and the cooling elements is solidified by cooling.

This is a division of application Ser. No. 93,165 filed Nov. 27, 1970, now US. Pat. No. 3,709,648.

SUMMARY OF THE INVENTION This invention relates in general to a method for producing solid blocks from sodium hydroxide solution and in particular to a new and useful method wherein a solution of sodium hydroxide is fed to a shaft and is cooled at the top of the shaft as the previously solidified hydroxide is moved downwardly directly after it is formed, and is subsequently cut into blocks as it exits from the shaft.

Sodium hydroxide or lye in crystalline form is a commercial product. The flakes, pellets or grains of the sodium hydroxide which are frequently produced require a relatively large and expensive packing because of the relatively large bulk weight of about 1 kg./ltr., and they also render transportaion difiicult. In a known method, a molten lye is filled in barrels which serve after the solidification of the lye as a packing therefor. The usual round barrels, however, also require relatively much transportation space and are heavy and expensive besides. In order to avoid these disadvantages a continuous method has been proposed where the liquid lye is forced through a prismatic horizontal shaping and cooling shaft. The solid lye extrusion which leaves the shaft is subsequently cut up into individual blocks. Since, with this method, only a circumferential portion of the Wall of the shaft is available for cooling, it is necessary, because of the poor heat transfer of the crystallizing lye, to make the shaft cross section relatively small and this leads to correspondingly small block dimensions. If, additionally, cooling ribs engaging into the solid lye formation and forming grooves in the same are provided on the shaft wall, this, of course, results in a better cooling of the formation core but it necessarily leads to a Worse weight volume ratio of the finished blocks. In addition, it increases the friction of the formation in the shaft to such an extent that pressure heads of over 60 atmospheres excess pressure would be required to be able to push the lye solidifying in the shaft through the shaft. The absence of economical delivery pumper for such high pressures and which will withstand the aggressive lye in permanent operation makes this method virtually impractical.

In accordance with the methods of the invention, the disadvantages of the prior art are avoided. With the invention, the molten lye is supplied by gravity to a vertical cooling shaft and it is cooled successively from above by directing cooling elements downwardly into the shaft for cooling the liquid lye as it is supplied in each successive step. The elements are moved downwardly sufiiciently to cause the ejection of the solidified extrusion from the lower end of the shaft during each cooling step movement. After each extraction of the cooling elements, the shaft is again filled up to the original level by gravity infeed and at least a portion of the refill liquid melt which is present between the solidified extrusion and the cooling elements is solidified by the next cooling step in which the elements are again moved downwardly into the tower.

The filling or refilling of the vertical shaft by gravity permits elimination of the trouble prone pressure pump. The dead weight of the extrusion which solidifies in the shaft also contributes to each ejection. The ejection steps, and hence the quantity of refill melt which will be solidified during each step by the cooling during each working stay or cycle, can be selected so small that, in particular owing to the cooling elements acting from above, rapid solidification of the refill melt is attained, even at large shaft cross sections. A large shaft cross section means a large extrusion cross section to that of relatively large blocks weighing for example, of 50 kg. can be produced.

The apparatus for practicing the method advantageously includes a solidifying tower or shaft having means at the upper end thereof for cooling the Wall around the circumference and also having means at the top for heating this portion of the top to maintain a liquid condition in the event that it is necessary for the movement operation of the cooling elements. The cooling elements themselves comprise one or more fixed elements and/ or one or more movable elements which may be moved into and out of the top during each cooling cycle of operation. The individual cooling elements are tapered downwardly to a point to facilitate the downward movement of the extrusion which is formed and the lower end of the shaft carries cutting means for severing the solid material which it moved out of the shaft and after it is accumulated to a desired block size.

Accordingly, it is an object of the invention to provide an improved method for forming solid blocks of lye from a liquid melt of the lye and using one or more movable cooling elements and a cooling shaft comprising cooling a quantity of the liquid lye by contacting the lye from above its surface with the cooling elements to solidify the liquid lye and to direct the solidified lye downwardly immediately after it is frozen, and repeating the movement of the cooling elements first out of the association with the solid lye to leave a space for the inflow of additional liquid lye and then downwardly into association with the fresh liquid lye to solidify it and direct it downwardly until a quantity of the solidified lye is accumulated below the lower end of the shaft and thereafter cutting the accumulated solidified lye into blocks.

A further object of the invention is to provide a method of solidifying liquid lye which uses a vertically elongated tower or shaft opened at the top and the bottom and having a means for feeding liquid lye by gravity into the top thereof and using one or more movable cooling members, comprising directing the cooling members downwardly into the tower from above to cool a quantity of the liquid lye therein and subsequently pushing the solidified lye downwardly so as to cause the eventual outward movement of the lye from the bottom of the tower, withdrawing the cooling member and permitting the liquid lye to feed by gravity into the tower above the solid lye to a predetermined height level, and thereafter again advancing the cooling member into association with the liquid lye to freeze it and to move the newly frozen lye and the already solid lye downwardly in the tower.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a partial vertical section of a device for solidifying sodium hydroxide constructed in accordance with the invention;

FIG. 2 is a section similar to FIG. 1 but rotates 90 degrees in relation to FIG. 1; and

FIG. 3 is a section taken on the line IIIIII of FIG. 1.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in particular, the invention embodied therein comprises a vertical shaft or tower generally designated 1 which is in the form of a flat cylinder and which is open at the top and the bottom or at both ends in the event that the shaft is arranged horizontally.

The shaft 1 includes a hollow jacket or cooling medium flow space 2 adjacent the upper end for aiding in the cooling and solidifying of the sodium hydroxide. Above the cooling jacket 2 and directly adjacent the top of the shaft 1 are a plurality of coils 5 which provide means for heating this area of the shaft.

In accordance with a feature of the invention, liquid lye is supplied from a lye tank 4 through a gravity feed line 3 to the upper portion of the shaft 1. The lye feeds downwardly through the line 3 to fill the shaft 1 to a predetermined level of operation during each cooling step.

The lower end of the shaft 1 is provided with cutting means in the form of a severing device or a double knife 6 as shown in FIG. 2. The lower end of the shaft 1 is arranged above a curved guide plate 7 which has a lower end oriented directly adjacent a roller conveyor 8 so that the severed solid blocks 14 of lye are delivered from the shaft 1 through a curved guide and onto the conveyor 8.

Cooling means are associated with the top of the shaft 1 and include a plurality of laterally spaced fixed cooling elements 12b and a plurality of movable cooling elements 12a arranged alternately with the fixed elements. The movable elements 12a are carried on a traverse or cross beam 11 which is secured to a piston rod 10a of a piston 10 which is movable in a fluid cylinder 19 located in a fixed position above the shaft 1. The fluid cylinder 19 and piston 10 combination comprises pusher means 97 The movable piston 10 comprises a pushing device to cyclically shift the movable cooling elements 12a from the solid line position indicated upwardly to the dotted line position of the cross member 11 shown in FIG. 1 and then back downwardly again for the next cycle of operation. All of the cooling elements 12a and the cooling elements 12b are tapered downwardly toward a point and are formed as individual conical members in order to facilitate their engagement and disengagement from the solid lye material which is formed during the operation. Depending on the size of the shaft cross section two or more rows of movable cooling elements 12a and fixed cooling elements 12b are provided. The hollow cooling elements 12a and 12b are connected with a cooling medium, lines 15a and 15b, respectively which supply the cooling medium thereto. As the cooling medium for the jacket 2 and for the elements 12a and 12b ordinary water may be used, for example.

METHOD OF OPERATION When the device is to be operated for the first time, the shaft 1 must be temporarily closed at the bottom and the molten sodium hydroxide supplied from the tank 4 to feed by gravity up to the filling level indicated at the top. Since not only the layers of the melt or liquid sodium hydroxide which fill close to the walls are cooled but also, due to the cooling elements immersed in the liquid melt, the core portions of the filling are also cooled, the melt will solidify after a short period of time. After the movable elements 12a first contact the portion of the melt which is still liquid at the top they solidify this portion and, upon continued downward movement, cause the whole lowermost solidified portion to be moved downwardly in the shaft as indicated at 13.

The pushing means 9 are operated to alternately raise and lower the cooling elements 12a They are raised by a relatively small amount, for example a few cm., and the fixed cooling elements 12b prevent the solidified lye from moving upwardly therewith. solidification of the uppermost layer of lye in the shaft 1 is uprevented by heating coil 5 Which surrounds the upper shaft portion.

During the lifting portion of the cycle when the in dividual elements 12a are moved upwardly, there is an annular layer of conical form which is emptied as indicated by the dotted line shown in FIG. 1 and this is immediately filled up with the liquid at the top of the shaft 1. This melt which flows into this annular gap forms only a thin layer around the cooling elements 12a and as these elements are brought into contact therewith it is immediately solidified.

With the solidified lye present around each of the elements there is again a downward movement of the movable elements 12a, but in so doing the lye is detached from the fixed cooling elements 12b and moved down wardly with the remainder 13 in the shaft 1. The displacement of the solid part 13 from the remainder forms an immediate gap around the fixed elements 12b which is immediately filled with additional liquid which is replenished by the gravity feed from the tank 4. Once again, the cooling elements 12a are lifted to form gaps which can be filled with a liquid sodium hydroxide and hence then they are moved downwardly to advance the solid lye 13 downwardly in the shaft and this continues in repeated succession. The lye extrusion or solid material 13 continuously emerges from the lower end of the shaft 1 step by step. When a suflicient quantity of the lye 13 passes the severing device 6, it is cut up into a single block 14 of the desired length and this block falls on the guide plate 7 which deflects it onto the conveyor 8. From the conveyor 8 it is fed to a packaging station (not shown) where the blocks are packed, for example, in plastic foils.

The described method is simple in operation. Despite the division of the process into several individual steps the continuous block production method is obtained. High pressure pumps and their associated values and packings are not required. With such, a method it is possible to obtain block forms and block sizes most favorable for transporation and handling, weighing, for example, kg. add more, independence on the form and size of the shaft cross section and the number and arrangement of the cooling elements which are immersed in the shaft from above. The cooling time in the individual cooling steps depends only on the selected lifting or lowering path of the cooling elements, that is, on the size of the particular annular gaps produced and not on the size of the block or shaft cross section. The heat transfer paths from the melt to the cooling face can be maintained correspondingly small.

What is claimed is:

1. A method of producing solid blocks from a liquid such as molten sodium hydroxide, comprising the steps of providing an upright shaft open at both ends; initially blocking the lower end of the shaft; filling the shaft to a predetermined level with the liquid; positioning at least one stationary downwardly tapered cooling element and at least one upwardly and downwardly movable downwardly tapered cooling element in the liquid at the upper end of the shaft; cooling the liquid in the shaft to form a solid; unblocking the lower end of the shaft; supplying the liquid to the shaft above the formed solid; at least partially retracting each movable cooling element upwardly from the solid for flow of the liquid into the space between each movable cooling element and the solid to solidify the liquid in contact with each movable cooling element; then moving each movable cooling element downwardly to force the solid downwardly in the shaft to leave a space between each stationary cooling element and the solid for receipt and solidification of additional liquid in contact with the stationary cooling element; each stationary cooling element blocks upward movement of the solid during retraction of each movable cooling element upwardly of the shaft; and cyclically repeating the upward and downward movement of each movable cooling element to force a continuous length of the solid out of the lower end of the shaft.

2. A method of producing solid blocks from a liquid, as claimed in claim 1, including severing the continuous length of the solid forced out of the lower end of the shaft into blocks.

3. A method of producing solid blocks from a liquid, as claimed in claim 1, including the step of continuously replenishing the liquid in the upper end of the shaft by gravity flow of the liquid.

4. A method of producing solid blocks from the liquid, as claimed in claim 1, including maintaining the liquid at the upper end of the shaft above the solid and adjacent each cooling member in a liquid condition.

5. A method of producing solid blocks from a liquid, as claimed in claim 4, including cooling the shaft externally at a zone spaced downwardly from its upper end to cool and solidify the liquid in the shaft.

References Cited UNITED STATES PATENTS 3,658,116 4/1972 Hunt 164283 MX 2,639,594 5/1953 Watt 62-71 X FOREIGN PATENTS 750,131 6/1956 Great Britain 164-283 M ROBERT F. WHITE, Primary Examiner T. P. PAVELKO, Assistant Examiner US. Cl. X.R. 

1. A METHOD OF PRODUCING SOLID BLOCKS FROM A LIQUID SUCH AS MOLTEN SODIUM HYDROXIDE, COMPRISING THE STEPS OF PROVIDING AN UPRIGHT SHAFT OPEN AT BOTH ENDS; INITIALLY BLOCKING THE LOWER END OF THE SHAFT; FILLING THE SHAFT TO A PREDETERMINED LEVEL WITH THE LIQUID; POSITIONING AT LEAST ONE STATIONARY DOWNWARDLY TAPERED COOLING ELEMENT AND AT LEAST ONE UPWARDLY AND DOWNARDLY MOVABLE DOWNWARDLY TAPERED COOLING ELEMENT IN THE LIQUID AT THE UPPER END OF THE SHAFT; COOLING THE LIQUID IN THE SHAFT TO FORM A SOLID; UNBLOCKING THE LOWER END OF THE SHAFT; SUPPLYING THE LIQUID TO THE SHAFT ABOVE THE FORMED SOLID; AT LEAST PARTIALLY RETRACTING EACH MOVABLE COOLING ELEMENT UPWARDLY FROM THE SOLID FOR FLOW OF THE LIQUID INTO THE SPACE BETWEEN EACH MOVABLE COOLING ELEMENT AND THE SOLID TO SOLIDIFY THE LIQUID IN CONTACT WITH EACH MOVABLE COOLING ELEMENT; THEN MOVING EACH MOVABLE COOLING ELEMENT AND THE WARDLY TO FORCE THE SOLID DOWNWARDLY IN THE SHAFT TO LEAVE A SPACE BETWEEN EACH STATIONARY COOLING ELEMENT AND THE SOLID FOR RECEIPT AND SOLIDIFICATION OF ADDITIONAL LIQUID IN CONTACT WITH THE STATIONARY COOLING ELEMENT; EACH STATIONARY COOLING ELEMENT BLOCKS UPWARD MOVEMENT OF THE SOLID DURING RETRACTION OF EACH MOVABLE COOLING ELEMENT UPWARDLY OF THE SHAFT; AND CYCLICALLY REPEATING THE UPWARD AND DOWNWARD MOVEMENT OF EACH MOVABLE COOLING ELEMENT TO FORCE A CONTINUOUS LENGTH OF THE SOLID OUT OF THE LOWER END OF THE SHAFT. 